Compact, 1.5 A Linear Charger
for Single-Cell Li+ Battery

ADP2291



Rev. 0
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FEATURES
Simple, safe linear charger for single cell lithium battery
4.5 V to 12 V input voltage range
Adjustable charging current up to 1.5 A
Low cost PNP external pass element
Automatic reverse isolation with no external blocking diode
Output overshoot protection
Deep discharge precharge mode
Thermal shutdown
Automatic recharge
Programmable termination timer
LED charging status indicator
4.2 V output voltage with ±1% accuracy over line and
temperature
1 µA shutdown supply current
Small, 8-pin MSOP and 3 × 3 mm LFCSP packages

APPLICATIONS
Wireless handsets
Smart handhelds and PDAs
Digital cameras
Single cell lithium ion-powered systems
Cradle chargers

GENERAL DESCRIPTION
The ADP2291 is a constant-current/constant-voltage linear
charger for a single cell lithium ion battery, requiring just a few
components to provide a simple and safe charging system that
operates from a wide 4.5 V to 12 V input voltage range. It
features an internally controlled, multistep charging cycle that
improves battery life.
An external, low cost, PNP provides the charging current to the
battery and an external resistor sets the maximum charge
current. A small external capacitor programs the maximum
charge time. The controller includes an LED driver to indicate
the battery charging status.
Safety features include charging stop mode for battery faults,
output overshoot protection, and thermal shutdown. The
ADP2291 also features automatic reverse isolation, which does
not require an additional blocking diode.
The multistep charge cycle optimizes the battery charging time
in a safe manner. It features a trickle charge mode for a deeply
discharged cell and a fast charging mode with a maximum
current of 1.5 A. The ADP2291 controls the end of charge with
a 4.2 V output voltage that is 1% accurate over line and temp-
erature. It automatically recharges the battery if the cell voltage
drops. When the input supply is removed, the part enters a low
current state and reduces the current drawn from the battery to
below 1 µA.
The ADP2291 is available in both a small, 8-pin MSOP package
and a 3 × 3 mm LFCSP package that is ideally suited for small,
portable applications.

TYPICAL OPERATING CIRCUIT
ADP2291
TIMER ADJ
RS Q1
CTIMER
INPUT
4.6V–12V
SHUTDOWN
+
IN
CHG
BAT
CIN
GND
CS DRV
COUT
04873-0-001

Figure 1. Basic Circuit Configuration